A fuel cell is configured to electrochemically react a hydrogen-containing fuel gas obtained by reforming a material gas, such as a city gas, with an oxygen-containing oxidizing gas, such as air, to generate electric power and heat at the same time. A unit cell (cell) of the fuel cell includes an MEA (Membrane-Electrode-Assembly) constituted by a polymer electrolyte membrane and a pair of gas diffusion electrodes, gaskets, and electrically-conductive separators. A groove-like gas channel which allows the fuel gas or the oxidizing gas (each of these is referred to as a “reactant gas”) to flow therethrough is formed on a main surface of each separator which surface contacts the gas diffusion electrode. Then, the gaskets are disposed around a peripheral portion of the MEA, and a pair of separators sandwich the MEA. Thus, the cell is configured.
Known as a method for manufacturing such cell of the fuel cell is a method for manufacturing the polymer electrolyte fuel cell which is improved in assembling (see Patent Document 1 for example).
FIG. 15 is a schematic diagram showing an outline of a step (a catalyst layer applying step 310 and a diffusion layer integrating step 320) of manufacturing the cell disclosed in Patent Document 1.
As shown in FIG. 15, in the catalyst layer applying step 310 in this fuel cell manufacturing method, catalyst layers 331 are formed on a polymer electrolyte membrane 330, and a catalyst layer-polymer electrolyte assembly 332 is integrated using hot rolls 380. Then, in the diffusion layer integrating step 320 in this fuel cell manufacturing method, diffusion layers 333 are disposed on both surfaces, respectively, of the catalyst layer-polymer electrolyte assembly 332, and the diffusion layers are joined to the catalyst layer-polymer electrolyte assembly 332 by hot rolls 390. With this, an operation of assembling the cell is simplified.
A common fuel cell is a so-called stack-type fuel cell in which the cells are stacked and fastened, and adjacent MEAs are electrically connected to each other in series. When manufacturing a cell stack, the stacked cells are sandwiched between end plates, and the end plates and the cells are fastened by fasteners. Therefore, the polymer electrolyte membrane has to have an adequate strength in order to endure pressure of the fastening and to avoid physical damages caused by, for example, abrasion in long-term use.
To such needs, known is a seal structure of a solid polymer electrolyte fuel cell in which a frame-shaped protective membrane is attached to the polymer electrolyte membrane (see Patent Document 2 for example).
FIG. 16 is a schematic diagram showing an outline of the seal structure of the solid polymer electrolyte fuel cell disclosed in Patent Document 2.
As shown in FIG. 16, a frame-shaped protective membrane 220 formed by a fluorocarbon resin-based sheet is disposed on a main surface of the solid polymer electrolyte membrane 210 such that an inner peripheral portion thereof is covered with an electrode 213. In addition, a gas sealing member 212 is disposed to surround the electrode 213 such that a gap 214 is formed between the gas sealing member 212 and the electrode 213. With this, since the protective membrane 220 is sandwiched between the gas sealing member 212 and the solid polymer electrolyte membrane 210 and between the electrode 213 and the solid polymer electrolyte membrane 210, and the protective membrane 220 reinforces the solid polymer electrolyte membrane 210 at the gap 214, it is possible to prevent the solid polymer electrolyte membrane 210 from being damaged without increasing the thickness of the solid polymer electrolyte membrane 210.
Patent Document 1: Japanese Laid-Open Patent Application Publication 2001-236971
Patent Document 2: Japanese Laid-Open Patent Application Publication Hei 5-21077